Please help with this practice problem I am having difficulty with. I will leave a review and thumbs up, thank you in advance!

Capital Asset Pricing Model Assume the CAPM holds. The expected return of the market portfolio is 15% and its standard deviation is 20%. The T-bill rate is 5%. What is the standard deviation of an efficient portfolio that has an expected return of 10%? Capital Asset Pricing Model Assume the CAPM holds. The expected return of the market portfolio is 15% and its standard deviation is 20%. The T-bill rate is 5%. What is the standard deviation of an efficient portfolio that has an expected return of 10%